Space resonant system



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`lune 25, 1957 Filed Sept. l5. 1954 B. J. MIDLOCK y SPACE REsoNANT SYSTEM SEARCH ROUE atnt Oice 2,797,324 Patented June 25, 1957 SPACE RESNANT SYSTEM Bernard J. Midlock, Norwalk, Conn., assignor to Eastern Industries, Incorporated, East Norwalk, Conn., a corporation of Delaware Application September 15, 1954, Serial No. 456,242

Claims. (Cl. Z50- 36) This invention relates to a system for the production of ultra high frequency voltages, and particularly to a system in which greater power output is obtained. The invention has been found to be of particular advantage in reentrant oscillators employing the type 2G40 lighthouse tube.

One of the objects of this invention is to provide a new improved ultra high frequency space resonant system. Another object of this invention is to provide for improved utilization of the lighthouse type tube frequently used in such systems.

A further object of this invention is to provide for greater power output in an ultra high frequency voltage system through use of redesigned coupling structure.

An additional object of this invention is to provide for more efficient power output in an ultra high frequency oscillator system of the lighthouse tube and associated cavity resonator type through use of an improved coupling structure.

It is also an object of this invention to provide an improved ultra high frequency oscillator system employing a lighthouse type tube and associated cavity resonator with an improved coupling structure whereby substantially linear variation or amplitude modulation of output power may be obtained at substantially constant frequency by varying the anode voltage.

The previously used high frequency systems had the disability of having a low power output, thus resulting in low etliciency and difficulty in obtaining sufficient output for some applications. The device of my invention modifies the resonant cavities associated with the lighthouse type tube used in high frequency systems to correct such deficiency. In general, it utilizes a shielding member Which improves the output of the system by increased feedback coupling or otherwise. This shielding member preferably is in the form of a cathode sleeve as more fully set forth below. The result is a manifold increase of power output for a given anode voltage over a considerable range of such voltage, enabling a considerably higher power output to be obtained at a considerably lower anode voltage in a re-entrant oscillator employing a 2G40 tube at a constant frequency of about 2455 megacycles and modiiied by use of the cathode sleeve in accordance with the present invention for example.

This invention is described below with reference to the accompanying drawings.

Fig. l is a sectional view showing a lighthouse type tube in a space resonant system in accordance with the teachings of my invention.

Fig. 2 is a sectional view taken on line 2-2 of Fig. l.

Referring especially to Fig. l, it will be seen that the tube 1 utilized is of the well-known lighthouse type, exempliied for instance by tube 2G40. This tube has a base 2, cathode connection shell 3, grid disk 4 and anode 5. As is customary in tubes of this nature, the cathode, grid, and anode are insulated from each other by glass walls 6, having metal to glass seals at the points of junction,

in order that the tube may be evacuated in the usual manner.

The space resonant system of this invention is preferably that of a re-entrant oscillator with certain modifications. The overall assembly of concentric cylinders into which the tube 1 is inserted may be referred to as a cavity resonator, which is modified from its usual form to incorporate the cathode sleeve or shielding member of the invention.

A conducting anode rod 9 serves to connect the anode 5 with the anode voltage supply 28, narrow slots 9 in the left end of rod 9 permitting this rod to grip the anode terminal 5 in the usual manner. A grid sleeve 8 of cylindrical shape and of conducting material is electrically connected to grid disk 4 by grooved contact fingers formed by narrow slots 8 in the usual manner and surrounds the major portion of anode rod 9 in addition to anode 5. The grid sleeve 8 extends a portion of the way to the left of the grid disk 4 toward cathode shell 3 in the usual manner.

Encircling grid sleeve 8 and anode rod 9 is a cathode cylinder 10 of the usual type. This cylinder is of conducting material and terminates at its cathode end in cathode contact fingers 11. These fingers preferably do not contact the cathode shell 3 itself, as usually found in rep-entrant oscillators, but rather in the present case encircle a cathode coupling sleeve or shielding member 12 which in turn encircles the cathode shell 3. Sleeve 12 is cylindrical and is split or slotted or both and is of proper dimensions to securely lit about and in tight friction contact with cathode connection 3 of tube 1. Fingers 11 fit over and in sliding friction contact with cathode coupling sleeve 12, enabling the tube 1 together with the cathode sleeve 12 and grid cylinder 8 to be slid in and out of the cathode cylinder 10 along its lingers 11 for adjustment or replacement purposes.

An ordinary band type clamp (not shown) may be employed to encircle the fingers 11 to tighten or loosen the assembly as desired to maintain the tube and associated cathode cylinder in xed operating position or to adjust the relative positions for desired operation.

Connecting end plate 13 of cathode cylinder 10 serves to close the end of cylinder 10 to complete the resonant system. It has an opening in its center to fit about the anode rod insulating support 14 which is mounted about anode rod 9. Radio frequency capacitor plate 16 is secured about rod 9 inside of insulator 14 to complete the anode radio frequency return to the end plate 13 of the cathode cylinder 10. Plate 16 is insulated from end plate 13 by mica insulating washer 1S.

The cathode coupling sleeve 12, above referred to, is metallic and of a cylindrical shape mounted between the circular cathode connection 3 and the fingers 11 of the cathode cylinder 10. It extends into the resonant space defined by cathode cylinder 10 and grid sleeve 8, and in particular serves to largelyencircle and partially shield from the outer region of this resonant space, the gap between cathode 3 and the left end of grid sleeve 8. This conducting sleeve 12 thus serves to segregate into two concentric zones the resonant space formed between cathode cylinder 10 and grid sleeve 8 in the region adjacent lighthouse tube 1 and in particular in the radial area between cathode shell 3 and anode 5, while leaving open at the outer (righthand) end of sleeve 12, adjacent to grid cylinder 8, a path for feedback coupling or interaction of radio frequency energy between such resonant space and the grid-cathode region of the tube.

The various components of the oscillator circuit, that is, anode rod 9, grid sleeve 8, cathode cylinder 10, and cathode coupling sleeve 12, are preferably made of brass and are silver plated.

As shown in Figs. 1 and 2, grid contact finger 19 provides the connection for grid sleeve 8 through support screw 20 and resistor 23 to the outside surface of cathode cylinder 10 at point 24, providing the self-bias circuit for the tube 1. Mica insulating washer 21 and insulating bushing 22 serve to support screw 20 and contact finger 19 and to insulate them from contact with cylinder 10. Cathode coupling sleeve 12 has a slot 25 in it to allow for the passage of grid contact finger 19 from screw 20 to grid sleeve 8. The slot 25 may extend along the split opening for the full length of the sleeve and of sufficient width to accommodate and clear the contact linger 19 as shown, or in an alternative arrangement (not shown) the slot 25 may extend from a point suicient to clear the left side of the contact finger 19 to the outer or righthand end of the sleeve 12 in the resonant space, with the lefthand part of the sleeve 12 split or slotted to provide spring contact with the cathode shell 3. The full slot arrangement is preferred for convenience in assembly. It is obvious that the opening 25 could also be in the form of a small hole with contact finger 19 changed to a straight or substantially straight radial form to engage the grid cylinder under some slight pressure through the hole, but it will be appreciated that this would make assembly and disassembly more awkward and the slot arrangement is therefore preferred.

The output of the tube is obtained through the capacitor type output probe made up of outside conductor 29, capacitor plate 30, which faces the grid cylinder 8, and central conductor 31. This probe is supported in position by conducting bushing 32 passing through hole 33 in cathode cylinder 10. The coupling of the output probe to the oscillator circuit is increased by moving the output probe toward the anode rod 9. As is well known, the best coupling position for stable operation is slightly less than that for maximum output.

Except for the greatly improved output, the operation of thev space resonant system including the tube 1 is substantially the same as with a customary 1re-entrant oscillator, feedback being provided by the opening around the righthand end of grid sleeve 8, the positioning and length of the grid sleeve being the major frequency determining portion ofthe oscillator circuit. The area between the anode rod 9 and the inside of the grid sleeve 8 near the anode connection 5 is the output tank circuit. The greatest standing wave appears at the open end of the grid sleeve 8, making the grid sleeve a one half wave resonant line fore-shortened by the tube capacitance and inductance. Lengthening the grid sleeve will lower the frequency of oscillation; shortening will increase the frequency. A limited frequency shift to put the oscillator on a fixed frequency can be had by moving the 2C40 tube 1 so that a choke is formed by the anode 5 and anode rod 9. Moving tube 1 out of the cathode cylinder will increase the size of the choke to lower the frequency of operation of the oscillator.

Introducing the cathode coupling sleeve 12, previously described, into the feedback circuit places a control on the effect of the feedback voltage on the oscillator output. It has been found experimentally that the length of the cathode coupling sleeve 12 between its righthand end and its point of connection on cathode shell 3 at the righthand end of the latter is preferably of the order of one-eighth the wave-length of the oscillator frequency for frequencies of the order of 2455 megacycles for example. This length is slightly shorter than that which provides for maximum oscillator power output but accordingly assures stable operation. In addition, it has been found that the slight differences between tubes, circuit dimensions and output loads can be compensated for by the mechanical arrangement of the cathode coupling sleeve 12, and that having sleeve 12 have a sliding lit over cathode connection 3 and beneath the inside surface of the cathode cylinder contact ngers 11 permits the effective length of coupling sleeve 12 to be adjusted to make these compensations and to provide optimum oscillator operation. t

Although the theory upon which this invention works is not completely known, it has been my theory that the addition of a shielding member along the lines of cathode sleeve 12 would create an improved feedback circuit in the cathode sleeve-grid cylinder space, and might change the point of takeoff of the feedback energy to advantage. In any case whether or not this theory is correct, I have found through experimentation that the use of a sh1elding member such as cathode coupling sleeve 12 will 1ncrease the power output of a tube such as the 2G40 by a large percentage. Thus, for example, it was found that for an output frequency of 2455 megacycles the output was almost doubled for an anode voltage of volts and was substantially tripled for an anode voltage of volts, as compared with the output I was able to obtain with the same tube and cavity resonator assembly without the cathode sleeve 12 and with the cathode cylinder fingers directly in contact with the cathode shell 3 in the usual manner, or with a spacer ring of the same diameter and thickness as the cathode sleeve occupying the space between the fingers 11 and cathode shell 3 but short enough axially so as not to extend beyond the cathode shell 3 into the cavity resonator.

It was also found that the cathode sleeve enabled a substantially linear variation of the power output at a substantially constant radio frequency to be obtained in relation to anode Voltage change over a considerable range of the anode voltage, which indicates considerable advantage in this space resonant system if it is desired to employ amplitude modulation.

In accordance with the usual practice the cathode cylinder 10, at the return point 24 of the grid bias resistor 23 and at the negative return point 35 of the anode voltage supply 28, is connected by an external wire (not shown) to the cathode connection pins by way of the usual socket for such pins (not shown) at the tube base, since the cathode proper is otherwise separated from the cathode shell 3 for direct current by an ultra high frequency capacitance within the tube.

An example of the dimensioning of a resonant space system such as is described herein is that had for an output frequency of 2455 megacycles. Here the inside diameter of cathode cylinder 10 was one and seven-eighths inches, the length of this cylinder three and one-quarter inches. The grid sleeve 8 had a length of two and onesixteenth inches, its righthand end being one and threequarters inches from the grid disk 4. The grid sleeve 8 had an outside diameter of seven-eighths inches, and was slotted at its left end to provide contact lingers, with proper inside diameter and grooved in the usual manner as shown, so as to iit over and make electrical connection with the grid disk 4 around the periphery of the latter.

The cathode coupling sleeve 12 used had a total length of one and tive-thirty-seconds inches, and extended from the highthand end of the cathode shell 3 a distance of approximately fiVe-eighths of an inch, or about oneeighth wave length, approximating the position shown in Fig. 1.

The cathode sleeve 12 used had a relaxed diameter before being placed on the tube, of slightly less than one inch so that it expanded somewhat along slot 25 when placed over the cathode shell 3 of the tube, at which time it had an inside diameter slightly over one inch corresponding to the outside diameter of the cathode shell 3 of the tube, with a wall thickness of twenty-five thousandths of an inch and a slot width of somewhat over one-quarter inch at slot 25 for example.

The projection 36 shown iu Fig. 2 in the outer wall of the cathode sleeve 12 near the slot 25 may be in the form of a small stud or may preferably be in the form of an axially elongated projection, and it is designed to engage one of the slots between the contact fingers 11 of the cathode cylinder so as to index the slot 25 to clear the contact finger 19. The projection 36 may have an elongated length of about one-half inch for example, and is also positioned preferably so that the contact fingers 11 will 'straddle the slot 2S so that no one of these contact fingers 11 will fall entirely into the slot.

It will be obvious that if desired the righthand part of the cylindrical sleeve or shielding member 12 extending within the cavity resonator might be supported in some other manner, as by soldering to the radial left end wall of the cathode cylinder 10 for example, without having an extension at the left end of this sleeve between the cathode shell 3 and the lingers 11 of the cathode cylinder, and with the lefthand end wall of the cathode cylinder extending in further radially to have the lingers 11 in contact directly with the cathode shell 3 in the usual manner, but the continuous form of sleeve 12 extending between the lingers 11 and the cathode shell 3 for support as shown or previously described is preferred for convenience of assembly and disassembly as well as llexibility of adjustment.

It will be appreciated by those skilled in the art that the output probe 29-31 and its associated bushing 32, while shown in a preferred position in the drawing, may be located somewhat farther from or nearer to the end wall 31 in the cathode cylinder 10, but if the probe is near such end wall the probe may preferably extend much nearer to the anode rod 9 or may preferably be of the well known pick-off loop type instead of the capacitor type shown.

It will be further appreciated that the grid bias connection for grid sleeve 8 via contact finger 19 is shown at about 180 degrees from the output probe 29-31 around the circumference of the cathode cylinder 10 for convenience of illustration, but that the angular relation f these two connections around the cathode cylinder may be varied over a wide range in choosing the locations of these elements as desired.

It will also be appreciated that the several conducting members such as anode rod 9, grid cylinder 8, cathode cylinder 10 and its end plate 13, and cathode sleeve 12 and the like, while described as metallic in the preferred form, may comprise conducting surfaces on a nonconducting base or wall for example as an alternate form.

It will be understood that the anode of the tube comprises not only the cylindrical part, to which the reference character is directed, projecting to the right in Fig. 1 from the anode disk of the tube, but this anode al-so extends within the sealed part of the tube to the left of this anode disk, and this external projection part, serving for anode connection, is sometimes referred to as the anode post or the anode connection post.

For a description of several kinds of disk-seal tubes of the lighthouse type, reference may be had to an article entitled Microwave oscillators using disk-seal tubes by A. M. Gurewitsch and I. R. Whinnery, beginning at page 462 of the Proceedings of the Institute of Radio Engineers of May 1947, for example.

As can be seen from the above and as will be obvious to those skilled in the art, various modifications and uses of the within described invention may be readily made Without departing from the spirit thereof.

I claim:

l. An ultra-high frequency space resonant system for association with a lighthouse-type tube having anode, cathode and grid elements, said system including a plurality of space resonant regions substantially defined by central and outer conductive members and an intermediate conductive member for cooperation with said elements, and a conducting sleeve positioned adjacent and about said tube, said sleeve being electrically connected to said cathode element and directed generally alongside said grid element and between said intermediate conductive member and said outer conductive member, said sleeve and said several conductive members being substantially concentric with said tube and each other.

2. A device of the character described including a lighthouse-type tube having an anode, a cathode, and a grid, an anode connecting rod providing an electrical connection between said anode and a source of electrical potential, said rod being in substantial axial alignment with said anode, cathode and grid, a pair of cylindrical outer conductive members, concentric with each other and with said rod, the outer of said members being electrically connected to said cathode, and the inner of said members being electrically connected to said grid and insulated from said cathode, and a cathode coupling sleeve concentric with and between said members, said sleeve being electrically connected to said cathode and encircling the portion of said tube between said cathode and said grid.

3. A device of the character described including a lighthouse-type tube having an anode, a cathode, and a grid, an anode connecting rod providing an electrical connection between said anode and a source of electrical potential, said rod being in substantial axial alignment with said anode, cathode and grid, a pair of cylindrical conductive members, concentric with each other and with said rod, the outer of said members being electrically connected to said cathode, and the inner of said members being electrically connected to said grid and insulated from said cathode, and a cathode coupling sleeve concentric with and between said members, said sleeve being electrically connected to said cathode and encircling a portion of said tube between said cathode and said anode.

4. An ultra-high frequency space resonant system of the re-entrant oscillator type including a lighthouse-type tube having anode, grid and cathode elements, a plurality of generally concentric conducting members extending from the said anode, grid and cathode elements respectively and defining generally concentric space resonant regions for and about said tube to form a cavity resonator for said tube, and a conducting shielding member connected to said cathode extension member adjacent the cathode part of the tube and extending generally concentric with the other said conducting members between the grid extension member and the cathode extension member and alongside the grid-cathode region of the tube substantially to the anode portion of the tube- 5. In a re-entrant oscillator system of the ultra high frequency type employing a lighthouse-type tube having anode, grid and cathode, a central rod connecting with said anode, an outer cylinder extending outward from said cathode and coaxial with said rod to form an enclosure therewith for said tube, an intermediate cylinder extending from said grid coaxially with and between said rod and outer cylinder, and a generally cylindrical sleeve member extending from the cathode between the outer -cylinder and the intermediate cylinder and adjacent the latter alongside said tube and coaxial with said other members.

6. In a re-entrant oscillator system of the ultra high frequency type employing a lighthouse-type tube having anode, grid and cathode, a central rod connecting with said anode, an outer cylinder extending outward from said cathode and coaxial with said rod to form an enclosure therewith for said tube, an intermediate cylinder extending from said grid coaxially with and between said rod and outer cylinder, and a generally cylindrical sleeve member extending from the cathode between the outer cylinder and the intermediate cylinder and adjacent the latter alongside said tube and coaxial with said other members, said sleeve member being formed of tubing split along one side and expanded to provide a anode, grid, cathode and the usual coaxial external connecting surfaces therefor arranged from top of the tube to its base respectively, a central rod connecting with said anode surface, an outer cylinder extending outward from said cathode surface and coaxial with said rod to form an enclosure therewith for said tube, an intermediate cylinder extending from said grid surface coaxial with and between the rod and outer cylinder, and a generally cylindrical sleeve member extending from the cathode surface between the outer cylinder and the intermediate cylinder and adjacent the latter alongside (said tube and generally coaxial with said other members.

8. In a re-entrant oscillator system of the ultra high frequency type employing a lighthouse-type tube having anode, grid, cathode and the usual coaxial external connecting surfaces therefor arranged from top of the tube to its base respectively, a central rod connecting with said anode surface, an outer cylinder extending outward from said cathode surface and coaxial with said rod to form an enclosure therewith for said tube, an intermediate cylinder extending from said grid surface coaxial with and between the rod and outer cylinder, and a generally cylindrical sleeve member extending from the cathode surface between the outer cylinder and the intermediate cylinder and adjacent the latter alongside said tube and generally coaxial with said other members, said cylindrical sleeve member being formed with an aperture in its outer surface, and a connecting member extending through said aperture from said intermediate cylinder and through an opening in said outer cylinder to provide for grid bias connection.

9. A high frequency space resonant system comprising an electric discharge device having a plurality of enclosed electrodes including an anode, a cathode and a grid, a plurality of substantially concentric members connected respectively to said electrodes and defining anode-grid and grid-cathode space resonant regions, and a further concentric member adjacent said intermediate member and between said intermediate member and the concentric member associated with said cathode, said further concentric member extending from adjacent said cathode and subdividing said grid-cathode space resonant region to provide improved coupling between said regions.

10. In a re-entrant oscillator for frequencies of the order of 2455 megacycles employing a lighthouse tube of the type having a cathode at its base, an anode at its top and an intermediate grid, a central rod connected to said anode, an outer cylinder connected to said cathode and concentric to and forming an enclosure with said rod for said tube, an intermediate cylinder connected to said grid and concentric with and between said outer cylinder and rod, and a further generally cylindrical member connected to said cathode and outer cylinder adjacent the base of said tube and extending into said enclosure alongside and concentric with said tube a distance of the order of one eighth wave length and directed toward and in partially overlapping spaced relation with said intermediate cylinder.

References Cited in the le of this patent UNITED STATES PATENTS 1,928,408 Clavier Sept. 26, 1933 2,451,825 Guarrera Oct. 19, 1948 2,476,725 Gurewitsch July 19, 1949 

